The present invention provides novel vinyl ester resins prepared from epoxy resins of the co-oligomerization product of a polyphenol cyanate mixture and a polymaleimide, as well as cured compositions prepared from said vinyl ester resins.
Vinyl esters are the reaction product of about equivalent amounts of a monounsaturated monocarboxylic acid and a polyepoxide. One class of vinyl esters is described by Bearden in U.S. Pat. No. 3,367,992 where dicarboxylic acid half esters of hydroxyalkyl acrylates or methacrylates are reacted with polyepoxide resins. Bowen in U.S. Pat. Nos. 3,066,112 and 3,179,623 describes the preparation of vinyl esters from monocarboxylic acids such as acrylic and methacrylic acid. Bowen also describes alternate methods of preparation wherein a glycidyl methacrylate or acrylate is reacted with the sodium salt of a dihydric phenol such as bisphenol A. Vinyl ester resins based on epoxy novolac resins are described in U.S. Pat. No. 3,301,743 to Fekete et al. Fekete et al describes vinyl esters where the molecular weight of the polyepoxide is increased by reacting a dicarboxylic acid with the polyepoxide resin as well as acrylic acid, etc. in U.S. Pat. No. 3,256,226. Other functional compounds containing a group which is reactive with an epoxide group, such as an amine, mercaptan and the like, may be utilized in place of the dicarboxylic acid. All of the above-described compositions, which contain the characteristic linkages ##STR1## and terminal polymerizable vinylidene groups are classified as vinyl esters and are incorporated herein by reference.
The vinyl ester is typically combined with a reactive diluent, a copolymerizable vinyl monomer, to alter the viscosity of the mixture, to vary the properties of the cured coating, or for other known reasons. Most any vinyl monomer may be employed which is copolymerizable with the unsaturated groups of the vinyl ester. Such monomers include both monovinyl and polyvinyl monomers. Typical monomers include the alkenyl aromatic monomers such as styrene, .alpha.-methylstyrene, vinyltoluene, t-butyl styrene and the like; and alkyl and hydroxyalkyl esters of acrylic and methacrylic acid such as methyl, ethyl, propyl, butyl, cyclohexyl and hydroxyethyl, hydroxypropyl and hydroxybutyl acrylates and methacrylates. In addition to the above, other monomers are especially useful for ultra-violet light curable systems such as 2-acetoxyalkyl acrylates; pentaerythritol di-, tri- or tetra-acrylates and the like and may be added in any order.
The vinyl ester and copolymerizable vinyl monomer blend is a crosslinkable vinyl ester resin which is cured by mixing in a free radical forming catalyst in an amount ranging from 0.1 to about 5 percent by weight, preferably 1 to 2 percent by weight. Examples of these catalysts are benzoyl peroxide, tertiary butyl hydroperoxide, methylethylketone peroxide and the like. It is frequently of value to add an accelerator such as N,N-dimethylaniline, cobalt naphthenate and the like.
Preparation of vinyl ester resins containing triazine or both triazine and oxazoline groups is taught by Hefner, Jr. in U.S. Pat. No. 4,515,934. The compositions described therein are prepared by reacting (a) a polyepoxide containing triazine groups, or (b) a polyepoxide containing both triazine and oxazoline groups, or (c) a mixture of (a) and (b) above with (d) from about 0.75 to about 1, preferably from about 0.9 to about 1, mole of a monounsaturated monocarboxylic acid or mixture of monounsaturated monocarboxylic acids per epoxide group in the presence of (e) a suitable quantity of a suitable catalyst. The resultant vinyl esters are used to prepare curable (copolymerizable) vinyl ester and vinyl monomer formulations.
Preparation of vinyl ester resins of polyepoxides containing triazine groups and iminocarbamate linkages is taught by Hefner, Jr. in U.S. Pat. No. 4,555,554. The compositions described therein are prepared by reacting (a) a polyepoxide containing at least one triazine group and at least one iminocarbamate linkage with (b) from about 0.75 to about 1.2, preferably from about 0.9 to about 1, mole of a monounsaturated monocarboxylic acid or mixture of monounsaturated monocarboxylic acids per epoxide group in the presence of (c) a suitable quantity of a suitable catalyst. The resultant vinyl esters are used to prepare curable (copolymerizable) vinyl ester and vinyl monomer formulations.
The vinyl ester compositions of the present invention are derived by reaction of an epoxy resin of the co-oligomerization product of a polyphenol cyanate mixture and a polymaleimide with a monounsaturated monocarboxylic acid. The invention consists of the vinyl esters and the vinyl ester and copolymerizable vinyl monomer formulations, whether or not cured. The vinyl ester resin compositions of this invention possess improved mechanical properties, especially tensile and flexural strength, percent elongation and flexural modulus.